Invalid argument for 'pairs' (table expected, got string), but argument is a table?

I'm trying to issue a post request via RemoteFunction, but the in pairs() loop is not working.

I'm getting an error trying to tell me im using the incorrect datatype for the 'pairs', but the argument is a table.

Server script:

local http = game:GetService('HttpService')
local database = 'http://boomlings.com/database/'

game.ReplicatedStorage:WaitForChild('IssuePostRequest').OnServerInvoke = function(php, param)
    local data = ''

    for i, v in pairs(param) do
        data = data .. ('&%s=%s'):format(
            http:UrlEncode(i),
            http:UrlEncode(v)
        )
    end

    data = data:sub(2)
    print(data)

    local returned

    local success, eMes = pcall(function()
        returned = http:PostAsync(database..php, data, Enum.HttpContentType.ApplicationUrlEncoded, false)
    end)

    if success then
        return {'Success', returned}
    else
        return {'Error', eMes}
    end
end

Local script:

local CAS = game:GetService('ContextActionService')
local secretC = 'Wmfd2893bg7'

CAS:BindAction('Response', function()
    local response = game.ReplicatedStorage:WaitForChild('IssuePostRequest'):InvokeServer('getGJUserInfo20.php', {
        secret = secretC,
        targetAccountID = 7362432
    })

    if response[1] == 'Success' then
        print(response[2][3])
    else
        warn(response[2])
    end

end, false, 'e')

You are free to correct my Http code, because I am extremely new to it.